1. Technical Field
The present inventions relate to control for normally closed power semiconductor devices and, more particularly, relate to power supplies having normally closed power semiconductor devices.
2. Description of the Related Art
Most of the power semiconductors used for power conversion and processing are normally open (normally off). By normally off, when a normally off power semiconductor is not energized, no current will flow through it. This property lends itself to safe operation because if a control signal is not present, the power semiconductor doesn't conduct electricity.
In contrast, normally closed (normally on) devices, such as certain SiC or GaN, are on without being energized. Consequently in order to keep the power device off the control signal must be present. In most power conversion topologies, the power semiconductor device must be in off state when the main power is applied. A similar rule applies for the shutdown: the device must be kept activated until the main power source is removed. This introduces substantial problems to the power designer.
The present invention is illustrated by way of example and is not limited by the accompanying figures, in which like references indicate similar elements. Elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale.
The details of the preferred embodiments will be more readily understood from the following detailed description when read in conjunction with the accompanying drawings wherein:
The details of the preferred embodiments will be more readily understood from the following detailed description when read in conjunction with the accompanying drawings wherein: